The Hubble Space Telescope has resumed science operations approximately a month after a technical problem shut down command of the science instruments and transmission of science data to Earth.

Both the Advanced Camera for Surveys' solar blind channel — the part of the instrument unaffected by a 2007 electrical short — and Wide Field Camera 2 have been restored, returning the capabilities the telescope had before the equipment failure. The Hubble team released a new image, captured by Wide Field Camera 2 after the repair, on Oct. 30.

Engineers will also attempt to restart the Near Infrared Camera and Multi–Object Spectrometer cryocooler in early November.

On Sept. 27, 2008, a malfunction occurred in Hubble's Control Unit/Science Data Formatter (CU/SDF), which both relays commands to the science instruments and formats their data for transmission.

Hubble was designed with two CU/SDFs — one active and one unpowered backup that can be activated in case of a malfunction. Engineers have switched to the backup system.

The switch means Hubble will function normally but no longer have a backup unit within the system to guard against a future failure.

Due to the importance of the system, NASA is unwilling to leave Hubble without a backup. The CU/SDF is part of an overall "command and data handling" system that helps operate the telescope. The most likely outcome is the installation of a complete replacement command and data handling system during Servicing Mission 4. The system was designed to be replaced during a servicing mission if necessary.

NASA has a backup system on the ground that has to be checked, tested and delivered to Kennedy Space Center, a process that will delay the mission — previously scheduled for October 2008 — until early 2009.